First off, where did you get a $1 a minute??? An average size yard is about 10000 sq ft, a large is like 25000, and a small is like 2000. having not seen the property, 16000 sq ft with a 48in walk behind, i could mow in a little less than 40 minutes and i would charge $50. That is assuming that there is not a lot of obsticals in my way, and that it is not a steep slope. Back to the $1 a minute, i have found that it is best to look at the whole picture, because you have to think how far away the property is compared to all of the others, for example, one yard could be 25 minutes away, but only late you ten minutes to mow, so in total you would have 35 minutes, but $35 is to expensive. So all in all, price each job taking all variables into consideration!